Nederland, Colo. ? Michelle Jorgenson thought it was odd that her 8-year-old daughter Cheyenne – conceived with sperm from a mystery man known to Jorgenson only as Donor 3066 – was extremely sensitive to sound and walked on her toes.

Jorgenson started checking on the Internet and soon learned of at least six other children around the country who were fathered by 3066. And of those seven, she discovered to her alarm, two have autism, and two others, Cheyenne included, show signs of a sensory disorder tied closely to autism.

The children’s mothers located one another beginning a year ago through the Donor Sibling Registry, a Web site run out of this Colorado mountain town. It enables mothers artificially inseminated by the same donor – and children fathered by the same man – to find each other.

In this case, the women all used 3066, whose sperm was provided by the California Cryobank, based in Los Angeles.

“Pretty much you’re thinking this person has a perfect medical history,” said Jorgenson, who lives in Sacramento, Calif.

The mothers who were impregnated with 3066’s sperm have been frustrated in their attempts to find out more and confirm their suspicions that their children inherited their medical problems from him.

Joshua Elin, 9, meets his donor siblings, Cheyenne Jorgenson, 8, left, as Allyson Cross, 7, looks on during his arrival to their reunion June 25 in Fresno, Calif. All three children were conceived from the same sperm donor and their mothers located each other through the Donor Sibling Registry Web site.

Researchers do not know whether autism, a disorder that affects the ability to form normal social relationships and communicate with others, is a hereditary disease or an acquired illness, according to the Autism Society of America.

The Web site helped Jorgenson find Jenafer Elin, whose 9-year-old son, Joshua, another offspring of 3066, also is sensitive to noise and hates wearing clothing with tags. Cheyenne, Joshua and their 7-year-old half-sister, Allyson, and their mothers met in Fresno, Calif., this summer for a reunion.

Donor 3066 – a man of Norwegian and German descent and a member of the Screen Actors Guild – filled out a medical profile and reported only that his paternal grandmother had high blood pressure, Jorgenson said.

Cappy Rothman, medical director and co-founder of the California Cryobank, said 3066 has been put on “restricted” status – meaning women can still use his sperm but are warned that problems could arise in their children – because a child fathered by him was diagnosed with what Rothman described only as a “metabolic problem.”

Rothman said the sperm bank tests for major infectious illnesses such as hepatitis and HIV, but not more exotic medical conditions, and it is not required by law to do so. The sperm bank relies on donors to fill out medical histories extending back three generations.